Award details

Regulation of chiasma frequency and synapsis initiation in arabidopsis meiosis

Reference	BB/C512810/1
Principal Investigator / Supervisor	Professor Chris Franklin
Co-Investigators / Co-Supervisors	Dr G Jones
Institution	University of Birmingham
Department	Sch of Biosciences
Funding type	Research
Value (£)	268,363
Status	Completed
Type	Research Grant
Start date	05/03/2005
End date	04/03/2008
Duration	36 months

Abstract

Our recent analysis of an Arabidopsis mutant defective in the MutS homologue MSH4 has suggested that meiotic recombination involves two pathways. A MSH4 dependent pathway which accounts for the crossovers that exhibit interference and a second pathway which distributes crossovers at random. Recent studies in yeast also suggest the existence of two recombination pathways (at least), but our results represent the first report of this this in a higher eukaryote. In yeast the MSH4 associated complexes are thought to correspond to sites of synapsis initiation and all appear to progress to give crossovers. Our studies in Arabidopsis also suggest a similar relationship except that it appears that the number of MSH4 associated complexes is almost three-fold the number of crossovers. However, it also implies that there is a mechanism for ensuring that only an appropriate number of MSH4 containing complexes progress to give crossovers. Our hypothesis is that the high number of complexes in Arabidopsis is required to ensure timely synapsis. The specific aims of the project are as follows: To confirm if there are two (or more) meiotic recombination pathways in Arabidopsis. It is proposed that the residual non-interference crossovers are dependent on the MUS81 recombinase. We have identified a putative homologue of MUS81 and a corresponding mutant line. Hence the aim will be to determine the chiasma frequency and distribution in the mus81 mutant. In addition a msh4/mus81 double mutant will be constructed to determine if this knocks out all crossing over. If not this could suggest a further pathway is involved. To investigate if the MSH4 dependent recombinant pathway ensures the obligate chiasma in order to ensure accurate chromosome disjunction it is essential that each bivalent has at least one chiasma, referred to as the obligate chiasma. Thus if mutation of mus81, removes the approximately 15 per centage of crossovers that do not exhibit interference, then it will be possibleto determine if the residual MSH4 dependent crossovers are sufficient to account for the obligate chiasma. To establish the relationship between synapsis initiation and designation of crossovers immunolocalisation studies suggest that MSH4 associated complexes mark the sites of synapsis initiation. The aim is to confirm if this is indeed the case by manipulating the level of MSH4 expression and monitoring synapsis initiation and progression. The question of how crossovers are designated and their number regulated such that they represent only a subset of the synapsis initiation events will be addressed. We will determine the potential role of several key recombination proteins in crossover designation selection. These include the MutL homologues MLH3 and MLH1 together with MSH5 and BLM.

Summary

unavailable

Committee	Closed Committee - Genes & Developmental Biology (GDB)
Research Topics	X – not assigned to a current Research Topic
Research Priority	X – Research Priority information not available
Research Initiative	X - not in an Initiative
Funding Scheme	X – not Funded via a specific Funding Scheme

I accept the terms and conditions of use (opens in new window)

export PDF file

back to list new search